A method and an apparatus for producing a solar module with flexible solar cells, in particular flexible thin-film solar cells, are described here, as well as a solar module produced with such an apparatus and in accordance with such a method.
A solar module or photovoltaic module converts the light of the sun directly into electrical energy. By way of most important components it contains several solar cells. A solar module is characterised by its electrical power ratings (in particular open-circuit voltage and short-circuit current). These depend on the properties of the individual cells and on the interconnection of the solar cells within the module.
Ordinarily a solar module has, in addition to the electrically interconnected solar cells, an embedding material and a rear structure. A top layer serves for protection against mechanical influences and influences of weathering. The embedding material and the top layer have to be transparent, in order to keep absorption losses within the spectral range from 350 nm to 1150 nm, and hence efficiency losses of the silicon solar cells ordinarily employed for electric power generation, as slight as possible. The embedding material (for example, ethyl vinyl acetate (EVA) film) serves for bonding the module composite. EVA has to be melted down at about 150° C. This is where the crosslinking process begins which lasts for about 15 minutes to 30 minutes. By reason of this long process-time, hitherto EVA has had to be processed only discontinuously in a vacuum laminator. The processing parameters (time-dependent pressure and temperature curves) for EVA are very limited. Furthermore, EVA turns yellow under the action of UV light. Molten EVA also flows into the interstices of the solar cells that are electrically contacted or that are connected to conductive adhesives, and in the process is thermally crosslinked. The formation of air bubbles, resulting in diminution of the power ratings (power generated by the solar module), is avoided by a lamination under vacuum and/or mechanical pressure. The rear structure protects the solar cells and the embedding material from moisture and oxygen. In addition, it also serves as mechanical protection in the course of mounting the solar modules, and as electrical insulation. The rear structure may have been formed from glass or from a composite film.
A common variant in this connection is constituted by solar modules with crystalline solar cells which are configured as silicon solar cells with a size of approx. 10 cm×10 cm to 15 cm×15 cm and a thickness of approx. 0.3 mm and which are very fragile. Between 6 and 100 solar cells are combined here to form a solar module. However, this type of solar module consisting of crystalline solar cells is very material-intensive in production and requires extremely careful handling in the course of mounting. An alternative to this is constituted by solar modules with thin-film solar cells which are applied in several layers of different materials onto a carrier material. By way of carrier material, also called the substrate, use is made as a rule of glass, metal foil or plastic film. The glass-pane sizes and sheet web widths are determined by the respective production process. A customary size for glass substrates is 60 cm×100 cm or 60 cm×120 cm. Thin-film solar cells may—depending on the carrier material—be flexible, but they require protection against corrosion.